JSON数据返回{}，没有任何数据

var getfiles = function (context) {

  var scriptPath = '/var/names/myfolder';
  fs.readdir(scriptPath, function (err, files) {
    if (err) return context.sendJson(err, 404);
    var resultingJson = {};
    for (var j = 0; j < files.length; j++) {
      subfolder = scriptPath + files[j];
      console.log(files[j]);// prints art,creation
      fs.readdir(subfolder, function (err, fi) {

                //fi prints [artdetails.txt,artinfo.txt]
                        // [creationdetails.txt,create.txt]    
          //  console.log(files[j]);// prints undefined here

        resultingJson[files[j]] = fi;

      });

    }
    console.log(resultingJson); // returing {}

    context.sendJson(resultingJson, 200);
  });
}
var getfiles = function (context) {

  var scri